1. Field of the Invention
This invention relates generally to fiber optic systems and more particularly to a system and method for assembling optical components.
2. Description of the Background Art
An optical transmission system includes a number of optic components, such as a laser subassembly that contains the optical source (i.e., the laser) and a fiber subassembly that includes a portion of the fiber optic cable, that are coupled together to transmit the optical signal. Certain applications, such as pump modules, require high coupling efficiency between the fiber subassembly and the laser subassembly. To optimize coupling efficiency between these components, five degrees of freedom ideally should be controlled during the assembly process. These five degrees of freedom include of the relative linear positions of the fiber and laser subassemblies in the x, y and z directions (where the z-axis is defined to be the optical axis) and the relative angular positions of the fiber and laser subassemblies in the Θx and Θy directions.
Current assembly techniques do not control all five degrees of freedom. For example, direct coupling typically controls only three degrees of freedom, namely, the relative linear position of the fiber and laser subassemblies in the x, y and z directions. Such an approach results in a certain amount of angular misalignment between the fiber and laser subassemblies, leading to sub-optimal coupling efficiency. To increase coupling efficiency with current techniques, the transverse (i.e., linear) tolerances of the optic components must be very tight to reduce the amount of angular misalignment. Requiring tight tolerances substantially increases the complexity and cost of the assembly process.
Another drawback of current assembly techniques is that the distance between the fiber and laser subassemblies is purposefully kept short to reduce the amount of angular misalignment between the subassemblies. The short distance limits the usefulness of the resulting assembly because there is no free-space propagation path. Further, the short distance precludes inserting isolators, filters and the like between the fiber and laser subassemblies, further limiting the usefulness of the resulting assembly.
Attempts have been made to use coupling lenses to solve the problems described above. However, using coupling lenses also results in complex and costly assembly.